Polyphenyl thioether lubricating compositions

ABSTRACT

LUBRICATING COMPOSITIONS COMPRISING POLYPHENYL THIOETHERS, POLYPHENYL ETHERS-THIOETHERS OR MIXTURES THEROF AND CONTAINING SMALL AMOUNTS OF A PERFLUORO ALIPHATIC DIBASIC ACID HAVE IMPROVED LUBRICATING PROPERTIES. THESE COMPOSITIONS ARE USEFUL AS LUBRICANTS OVER WIDE TEMPERATURE RANGES.

United States Patent O1 3,677,944 POLYPHENYL THIOETHER LUBRICATING COMPOSITIONS Frank S. Clark, St. Louis, Mo., assignor to Monsanto Company, St. Louis, M0. N Drawing. Filed Dec. 28, 1970, Ser. No. 102,154

Int. Cl. C10m 1/38, 1/30 US. Cl. 25248.4 Claims ABSTRACT OF THE DISCLOSURE Lubricating compositions comprising polyphenyl thioethers, polyphenyl ethers-thioethers or mixtures thereof and containing small amounts of a perfluoro aliphatic dibasic acid have improved lubricating properties. These compositions are useful as lubricants over wide temperature ranges.

This invention relates to improved lubricating compositions comprising polyphenyl thioethers, mixed polyphenyl ethers-thioethers and mixtures thereof, containing from 3 to 8 aromatic groups and a small amount of a perfluoro aliphatic dibasic acid as a lubricating additive.

'Polyphenyl thioethers and polyphenyl ether-thioether combinations have found wide application as functional fluids due to their excellent thermal stability and lubricity. For example they have been found to be valuable as hydraulic fluids and as lubricants in motor operation, particularly in jet engines.

Development of synthetic base stocks such as the polyphenyl thioether has provided lubricant fluids which are useful at elevated temperature such as 400 to 500 F. It is known that one of the aspects in which the polyphenyl thioether base stocks are considered deficient is in their lubricating characteristics. These lubricating characteristics include the load-carrying abilities and wear properties, especially under conditions of high pressures and temperatures reached in the advance design aircraft engines. Thus there is a demand for polyphenyl thioethers having improved lubricity properties.

-An object of the present invention is to provide for improved lubricating compositions employing polyphenyl thioethers, polyphenyl ether-thioethers, or mixtures thereof as base stocks.

These and other objects will become evident upon consideration of the following specification and examples.

It has now been found that compositions consisting essentially of a major amount of a polyphenyl thioether base fluid having the formula tains 1 to 4 carbon atoms or a halogenated phenylene group wherein the halogen is fluorine, bromine or chlorine, and Y is selected from oxygen and sulfur but at least one of the Ys is sulfur and n is an integer having a Value of from 1 to 6 and an additive amount of a perfluorinated aliphatic dibasic acid, have unusual ability to lubricate under high loads at high temperatures.

The amount of the perfluoro aliphatic dibasic acid employed in the compositions of this invention can range from about 0.01 to about 0.2% by weight. It is preferred to employ the acids in the compositions of this invention in amounts of from about 0.05 to 0.1% by weight based upon the total composition. a

3,677,944 Patented July 18, 1972 ice wherein n is an integer of from 1 to 6. It is particularly preferred to employ perfluorinated dibasic acids of Formula I wherein n is an integer of from 2 to 4.

Illustrative of the perfluorinated dibasic acids represented by Formula I are, for example perfluoro malonic acid, perfluoro succinic acid, perfluoro glutaric acid, perfluoro adipic acid, perfluoro pimelic acid, and perfluoro suberic acid.

The improvement in lubricity characteristics achieved by the addition of the perfluoro aliphatic dibasic acid to the polyphenyl thioether base fluid is unusual and surprising. Wear on a simulated bearing surface is especially decreased at test temperatures of 640 F. whereas when the base fluid is tested without the additive the lubricity of the base' fluid is not sufficient and the fluid fails the test after a short time.

The polyphenyl thioethers employed in the composition of this invention have from 3 to 8 benzene rings and from 1 to 7 sulfur atoms with the sulfur atoms joining the benzene rings in chains as ether linkages.

By the term polyphenyl thioether" as used herein is meant a compound or physical mixture of compounds represented by Formula I. The term includes compounds wherein all of the Ys in Formula I are sulfur. The term also includes those compounds which contain both oxygen and sulfur linkages betwen the benzene rings.

The compositions of this invention contain a major amount of the polyphenyl thioether base stock, i.e., at least 50% by weight of the total composition comprises a polyphenyl thioether. It is preferred that at least 60% by weight of the composition be a polyphenyl thioether base stock and even more preferred that at least by weight of the total composition comprise a polyphenyl thioether.

Illustrations of the alkyl-substituents present in the phenyl and phenylene groups of the polyphenyl thioethers are for example, methyl, ethyl, propyl, butyl and the like. Illustrations of the alkoxy-substituents are, for example, methoxy, ethoxy, propoxy, butoxy and their isomers.

The compositions of this invention can also contain from 0.01 to 10% by weight of the total composition of -a dialkyl hydrogen phosphite extreme pressure additive. The dialkyl hydrogen phosphites useful are those wherein the alkyl groups contain from 1 to 12 carbon atoms. These alkyl groups are for example, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, hexyl, decyl, isodecyl, dodecyl and the like.

Illustrative of the polyphenyl thioethers which can be employed as base stocks for the compositions of this in vention are the bis(phenylmercapto)benzenes. For example bis (m-phenylmercapto) benzene bis (o-phenylmercapto)benzene bis (p-phenylmercapto) benzene bis (m-phenylmercaptophenyl) sulfide bis (o-phenylmercaptophenyl) sulfide bis (p-phenylmercaptophenyl) sulfide (m-pllfiieinylmercaptophenyl) (o-phenylmercaptophenyl) su e p-phenylmercapto-m'-phenylmercapto diphenyl sulfide o-bis(o-phenylmercaptophenylmercapto) benzene p-bis (p-phenylmercaptophenylmercapto) benzene p-bis (o-phenylmercaptophenyhnercapto)benzene p-bis(m-pheny1mercaptophenylmercapto)benzene m-bis (p-phenylmercaptophenylmercapto)benzene o-bis (p-phenylmercaptophenylmercapto) benzene and the like and mixtures thereof.

Illustrative of the mixed polyphenyl ether-thioether compounds which can be employed as base stocks in the compositions of this invention are for example,

o-phenylmercapto-m-phenoxy benzene p-phenylmercapto-o-phenoxy benzene m-phenoxy-p-phenylmercapto benzene o-phenylmercapto-p-phenoxydiphenyl sulfide o-phenylmercapto-m-phenoxydiphenyl sulfide o-phenoxy-m'-phenylmercaptodiphenyl sulfide m-phenoxy-p'-phenylmercaptodiphenyl sulfide -phenoxy-p'-phenylmercaptodiphenyl sulfide p-phenoxy-p-phenylmercaptodiphenyl sulfide o-phenoxy-o'-phenylmercaptodiphenyl sulfide o,o' -bis (phenylmercapto)diphenyl ether o-phenylmercapto-m-phenyhnercaptodiphenyl ether 'o phenylmercapto-p-phenylrnercaptodiphenyl ether m-(m-phenylmercaptophenylmercapto) (m-phenoxypheny1mercapto)benzene [m-(m-phenylmercaptophenylmercapto)phenyl] [m- (m-phenoxyphenylmercapto) phenyl] sulfide 3 (m-phenylmercaptophenylmercapto) -3'- (m-phenylmercaptophenoxy)diphenyl sulfide 3,3 -bis m-phenylmercaptophenylmercapto) diphenyl ether '3-(m-phenylmercaptophenylmercapto)-3'-(m-phenoxyphenoxy) diphenyl sulfide 4- (m-phenylmercaptophenylmercapto -4'- nil-phenylmercaptophen-oxy) diphenyl ether 3- (m-phenylmercaptophenylmercapto) -3'- (m-phenoxyphenylmercapto) diphenyl ether 4,4'-bis(m-phenylmercaptophenoxy)diphenyl sulfide 4,4'-bis(m-phenoxyphenylmercapto)diphenyl sulfide 3 m-phenoxyphenylmercapto) -3 (m-phenylmercaptophenoxy)diphenyl sulfide 3,3-bis(m-phenylmercaptophenoxy)diphenyl ether '4- (m-phenylmercaptophenylmercapto)-4'-(m-phenoxyphenoxy)diphenyl ether 3- (p-phenylmercaptophenoxy) -3 (p-phenoxyphenoxy) diphenyl sulfide 3-(m-phenylmercaptophenoxy)-3'-(m-phenoxyphenylmercapto)diphenyl ether 3,3-bis(m-phenoxyphenylrnercapto)diphenyl ether and 3- (m-phenoxyphenylmercapto -3 (m-phenoxyphenoxy) diphenyl sulfide of 1 to 4 carbon atoms and halogen such as chlorine,

bromine and fluorine. Examples of such compounds are as follows:

4,4'-bis (m-trifiuoromethylphenylmercapto) diphenyl ether 3 ,4'-1b is m-trifluoromethylphenylmercapto diphenyl ether 2,3'-bis(m-trifluoromethylphenylmercapto)diphenyl ether 3,3'-bis(p-trifiuoromethylphenylmercapto)diphenyl ether 3,3'-bis (o-trifiuoromethylphenylmercapto)diphenyl ether 3,3'-bis(m-methoxyphenylmercapto)diphenyl ether 3,4'-bi's(rn-isopropoxyphenylmercapto)diphenyl ether 2-(m-tolyloxy)-2-phenylmercaptodiphenyl sulfide 2-(p-tolyloxy)-3'-phenylmercaptodiphenyl sulfide 2-(o-tolyloxy) -4'-phenylmercaptodiphenyl sulfide 3-(m-tolyloxy)-3'-phenylmercaptodiphenyl sulfide 3-(m-tolyloxy)-4'-phenylmercaptodiphenyl sulfide 4- (m-tolyloxy) -4'-phenylmercaptodiphenyl sulfide 3-xylyloxy-4-phenylmercaptodiphenyl sulfide 3-xylyloxy-3-phenylmercaptodiphenyl sulfide 3-phenoxy-3'-(m-tolylmercapto) diphenyl sulfide 3-phenoxy-4'(m-tolylmercapto)diphenyl sulfide 2-phenoxy-3'- (p-tolylmercapto)diphenyl sulfide 3-phenoxy-4'-(m-isopropylphenylmercapto)diphenyl sulfide 3-phenoxy-3 (m-isopropylphenylmercapto) diphenyl sulfide 3-m-toloxy-3'-(m-isopropylphenylmercapto1 diphenyl sulfide 4-(m-trifluoromethylphenoxy)-4-phenylmercaptodiphenyl sulfide 3- (m-trifiuoromethylphenoxy) -4'-phenylmercaptodiphenyl sulfide 2- (m-trifluoromethylphenoxy) -3 '-phenylmercaptodiphenyl sulfide 3 m-trifiuoromethylphenoxy) -3 '-phenylmercaptodiphenyl sulfide 3-(p-chlorophenoxy)-3-phenylmercaptodiphenyl sulfide 3- (m-bromophenoxy) -4-phenylmercaptodiphenyl sulfide bis[m-(m-chlorophenoxy)phenyl1sulfide m-bisE3-(p-methylphenylmercapto)phenoxy1benzene rn-bis[3-(m-trifluoromethylphenoxy)phenylmercapto]- benzene m-bis [3- m-bromophenoxy) phenylmercapto] benzene 3,3 '-bis[mp-methylphenylmercapto) phenoxy] diphenyl sulfide 3 A 3; [mp-methylphenylmercapto )phenoxy] diphenyl su e 3-(p-xenyloxy)-3'-phenylmercapto diphenyl sulfide,

EXAMPLE 1 A polyphenyl thioether-polyphenyl ether-thioether lubricant composition is prepared by combining perfluoro glutaric acid (0.10 gram) with grams of a thioether of the following composition:

Percent by wt. Meta-bis(phenylmercapto benzene 50 Bis (phenoxyphenyl) sulfide 12.5

( Phenoxyphenyl) (phenylmercaptophenyl) sulfide 23 .5 Bis (phenylmercaptophenyl)sulfide 12.65 3 ring and 5 ring thioethers -a--- 1.35

and containing 10 parts per million of a dimethyl silicone antifoam agent (Dow-Corning-ZOO, 350 cs. fluid). After stirring at 40 C. to dissolve the acid, the mixture is cooled to room temperature and filtered.

The resultant mixture was tested for lubricity on a high temperature wear machine. This machine comprises a steel shaft rotating on a silvered-bronze disc so that there is line contact between the shaft and the disc. This test simulates the cage wear of silver plated bronze bearing cages. A lever movable about an axis permits the test disc to be loaded against the test shaft. The heated steel shaft (640 F.) is rotated against the disc at 30,180 r.p.m.s at a load of 2.25 dekanewtons while the contacting surfaces are lubricated with the test oil at a flow rate of 1 ml. per minute. In the test the shaft requires 1 minute rotation to reach speed (30,180 r.p.m.) and is maintained at this speed for 5 minutes and is then allowed to coast to a stop (1 minute). The wear scar is then measured. A test failure is indicated by seizure of the shaft and disc or an excessive wear scar.

When the mixture of Example 1 was tested at 640 F. and also at 714 F. the shaft did not seize and the scar wear was not excessive.

When the base fluid was tested at 640 F. it failed the test.

The lubrication of the fluid from Example 1 was also shown with a slow speed four ball machine. A slow speed four ball machine measures the boundary lubricity action of additives. This test is a variation of the well known Shell Four Ball Test in which a ball is rotated against three stationary balls. Wear scars and/or seizure loads measure additive lubricity. In the slow speed instrument the three stationary balls are replaced with circular discs. Standard operating condition are:

3 kg. load 1 r.p.m. Room temperature to 700 F.

The speed of rotation is very low, namely one r.p.m. This equals 0.88 inch/minute. This is done for two reasons. It insures boundary conditions, i.e., metal to metal contact. It also eliminates metal skin temperature flashes which can occur at high speeds. Thus the bulk oil temperature is equivalent to the metal surface temperature. Under these conditions wear is negligible and friction is used to follow lubrication. After covering the ball and disc with the test oil, the initial friction is recorded. The test sample is then heated at 700 F. with continuous recording of the friction. This gives a boundary friction-temperature profile for the experimental fluid over this temperature range.

This mixture of Example 1 was tested by this procedure wherein R is a phenyl group or a substituted phenyl group, R is a phenylene group or substituted phenylene group, in which the substituents on said phenyl and phenylene groups are halogen, alkyl or alkoxy containing from 1 to 4 carbon atoms, In is an integer of from 1 to 6, Y is sulfur or oxygen provided that at least one of the groups represented by Y is sulfur, and mixtures of such thioethers and from about 0.01 to about 0.2% by weight of a perfluoro dibasic aliphatic acid of the formula wherein n is an integer of from 1 to 8.

'2. A composition of claim 1 wherein said perfluoro dibasic aliphatic acid is present in amounts of from about 0.05 to about 0.1% by weight.

3. A composition of claim 1 wherein said perfluoro dibasic aliphatic acid is perfluoroglutaric acid.

4. A composition of claim 2 wherein said perfluoro dibasic aliphatic acid is perfluoroglutanc acid.

5. A composition of claim 1 where n is from 1 to 3.

References Cited UNITED STATES PATENTS 2,262,773 11/1941 Lincoln et a1. 25254.6 3,284,355 1l/1966 P'apay 25254.6 X 3,412,140 11/1968 Seil et a1. 252-54.6 X 3,565,926 2/19'71 Furey 252--54.6 X 3,579,449 5/1971 Wann et a1 25254.6 X

FOREIGN PATENTS 10/ 1960 Great Britain.

DANIEL E. WYMAN, Primary Examiner W. H. CANNON, Assistant Examiner U.S. Cl. X.R. 25254.6 

